The invention relates to the processing of heavy hydrocarbon oils (hereinafter abbreviated to heavy oils) and, in particular, to a method of processing heavy oils which method comprises hydrotreating the oils at high temperature under high hydrogen pressure using a catalyst containing porous magnesium silicate as a major component to demetallize and simultaneously crack asphaltene in the oil and solvent deasphalting the hydrotreated oil, and which method leads to a light oil having a low metal content and being substantially free from asphaltene, and to an asphaltic residue having a low sulphur content and a high aromatic content.
It is known to carry out solvent deasphalting of heavy oil such as crude oil, tar, bitumen, topped crude or vacuum residue. Such heavy oils usually contain metals in the form of organic metal compounds (hereinafter abbreviated to soluble metals) and asphaltenes. The solvent deasphalting divides the heavy oil into a deasphalted oil and an asphaltic residue. The deasphalted oil generally has a comparatively low soluble metals content and a remarkably high reactivity in hydrodesulphurization or denitrogenation processes as compared to that of the raw heavy oil, so that it may be easily hydrotreated.
However, when a high reactivity of demetallization is required, or deasphalted oil is to be obtained in an extremely high yield, deactivation of the catalyst by deposition of metals or formation of coke or tar is unavoidable in the hydrotreatment of the deasphalted oil, because soluble metals and a fraction corresponding to carbon residue yet remain in the deasphalted oil in spite of being free from asphaltene. Moreover, a defect of this process is that the usefulness of the asphaltic residue is limited because soluble metals, asphaltenes, sulphur and nitrogen are concentrated in it. Moreover, attempts to decrease the amount of soluble metals in the deasphalted oil in order to make feasible the subsequent treatment of the deasphalted oil, tend to lower the yield of the deasphalted oil, increasing the asphaltic residue.
It has been proposed in, for example, U.S. Pat. No. 3,859,199 to hydrodesulphurize the heavy oil prior to solvent deasphalting. In this process the asphaltic residue obtained from the solvent deasphalting step is recycled to the hydrodesulphurization step. Although the nitrogen and sulphur contents in the deasphalted oil remarkably decrease, the sulphur and nitrogen contents in the asphaltic residue do not decrease. This limits the usefulness of the asphaltic residue obtained. Moreover, the activity of the hydrodesulphurization catalyst is remarkably degraded by the soluble metals, and chemical consumption of hydrogen necessary for the desulphurization step is remarkably high. Accordingly, this process seems to be not commercially useful.
To improve the situation stated above, the inventor has developed a sepiolite supported metal catalyst for hydrotreatment, such as selective demetallization of heavy oils and has described and claimed it in U.S. Pat. No. 4,152,250. Further application and development of the catalysts, supported on the above sepiolite and other porous magnesium silicate clay minerals, have been pursued in combination with other processings of heavy oil in order to utilize effectively various heavy oils and have been led to the present invention.